JP2007008132A - Dot position correction device, optical scanning device, image formation device, and color image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that variation in light emission levels of light sources directly leads to density variation of images, and reduction in the light emission levels due to characteristic deterioration of the light sources directly leads to image density reduction. <P>SOLUTION: This invention comprises a pixel clock generating unit 10 which generates a pixel clock of which phase is shifted by phase data indicating a phase shift amount of the pixel clock, means 10, 110 which perform dot position correction in a main scanning direction based on the phase shift of the pixel clock, and a means which uses a plurality of light sources having one main light source and one or more sub light sources as the light sources of an optical scanning device and performs dot position correction in a sub scanning direction by scanning on scanning lines wherein the main light source is different from the sub light source. The light emission timing of the light sources is generated based on the pixel clock generating unit 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dot position correction device and an optical scanning device used in an image forming apparatus such as a laser printer and a digital copying machine, and an image forming apparatus and a color image forming apparatus such as a laser printer and a digital copying machine.

  FIG. 19 shows a general configuration of an optical scanning device in an image forming apparatus such as a laser printer or a digital copying machine using an electrophotographic process. In this optical scanning device 400, laser light emitted from a semiconductor laser unit 401 as a light source is deflected and scanned (scanned) by a polygon mirror 402 as a rotating deflector, and is scanned through a scanning lens (fθ lens) 403. A light spot is formed by irradiating the photosensitive member 404, which is a scanning medium, and the photosensitive member 404 is scanned with the light spot in the main scanning direction for exposure. The photosensitive member 404 is rotationally driven by a driving unit (not shown), and is uniformly charged by a charging device (not shown), and then an electrostatic latent image is formed by exposure with the laser beam, and is developed by a developing device (not shown) to be a toner image. Is formed. The toner image on the photoreceptor 404 is transferred onto a transfer sheet by a transfer device (not shown), and the toner image is fixed to the transfer paper by a fixing device (not shown) and discharged to the outside.

  The photodetector 405 detects laser light incident from the polygon mirror 402 via the scanning lens (fθ lens) 403 before the image forming area of the photosensitive member 404, and the phase synchronization circuit 406 outputs from the clock generation circuit 407 for each line. Based on the clock, an image clock (pixel clock) set to a phase synchronized with the output signal of the photodetector 405 is generated and supplied to the image processing unit 408 and the laser driving circuit 409. The laser driving circuit 409 drives the semiconductor laser unit 401 according to the image data generated by the image processing unit 408 and the image clock whose phase is set for each line by the phase synchronization circuit 406, and the semiconductor laser of the semiconductor laser unit 401 is driven. The electrostatic latent image on the scanned medium 404 is controlled by controlling the light emission time.

However, in recent years, the demand for higher printing speed (image forming speed) and higher image quality has increased, and in response to this, the speed of a polygon motor that rotates a polygon mirror, which is a deflector, and the reference clock for semiconductor laser modulation are increased. However, both of these speeding-ups are approaching the limits, and the conventional technology cannot cope with them.
Further, in such an optical scanning device, the variation in the distance from the rotation axis of the deflecting / reflecting surface of the deflector such as a polygon mirror causes uneven scanning speed of the light spot (scanning beam) that scans the surface to be scanned. . This uneven scanning speed causes image fluctuations and degradation of image quality. For this reason, when high-quality image quality is required, it is necessary to correct scanning unevenness.

Therefore, in the optical scanning device, a plurality of laser beams (multi-beams) are emitted from the light source to the semiconductor laser unit, so that a plurality of laser beams from the scanning lens (fθ lens) are simultaneously scanned on the surface to be scanned in the main scanning direction. By adopting an optical scanning method using multi-beam scanning, higher speeds have been dealt with. In the multi-beam optical scanning method, the number of light beams that can be scanned simultaneously by the deflection of the deflector increases, so that the rotational speed of the polygon mirror, which is a deflector, and the pixel clock frequency can be reduced. Image formation is possible.
As a light source for generating the multi-beam, a method in which a single-beam laser chip is combined, a laser diode array (hereinafter referred to as an LD array) in which laser elements as a plurality of light sources are incorporated in one laser chip, a surface emitting laser, or the like Is used.

  FIG. 20 shows a usage example of the surface emitting laser used as the light source in the optical scanning device. When there is a surface emitting laser 410 in which a plurality of laser elements P1A, P1B, P1C, P1D, P2A, P2B, P2C, P2D... P4A, P4B, P4C, P4D are arranged in a lattice pattern in the x and y directions perpendicular to each other, A case will be considered in which the horizontal right-hand direction is the main scanning direction and the x and y axes are applied to the optical scanning apparatus with a certain angle with respect to the main scanning direction. At this time, as shown in FIG. 20, a plurality of dots can be simultaneously formed in the sub-scanning direction by the plurality of laser elements P1A to P4D, and high-speed and high-precision optical scanning is possible.

  A semiconductor laser such as an LD array as a light source for generating the multi-beam is extremely small and can be directly modulated at a high speed by a drive current, and thus has been widely used as a light source for a laser printer or the like in recent years. However, since the relationship between the drive current of the semiconductor laser and the optical output has a characteristic that varies depending on the temperature, it becomes a problem when the light intensity of the semiconductor laser is set to a desired value. In particular, in the case of a surface emitting laser in which a plurality of laser elements are configured on the same chip, the distance between each laser element is short, so the effects of temperature change and temperature crosstalk due to light emission and quenching of the laser elements are significant. It tends to cause fluctuations.

  Further, in the case of an optical scanning method using a multi-beam, if there is a difference in the oscillation wavelength of each laser element, an exposure position shift occurs in an optical system in which the chromatic aberration of the scanning lens is not corrected, and this corresponds to each laser element. Since the scanning width when the light spot scans the scanning medium varies for each laser element, which causes deterioration in image quality, it is necessary to correct the scanning width.

In the prior art, in an optical scanning device that scans a scanned medium with a plurality of light beams by arranging a plurality of light sources in a two-dimensional manner and deflecting the plurality of light beams with a deflector, crosstalk due to heat generation between light emitting points is generated. Patent Document 1 describes an example in which the arrangement density of light emitting points is maximized without causing an influence.
Further, in an image forming apparatus using a surface emitting laser, a method for controlling an electrostatic latent image of a pixel by having means for changing the light emission intensity of each chip and means for controlling a light emission time in units of pixels is disclosed in Patent Literature. 2.
Patent Document 3 describes a method of avoiding the problem of thermal stroke and realizing high density of recorded images by adopting a configuration in which the arrangement of light sources is defined in a scanning device using a surface emitting laser. ing.

JP 2001-272615 A JP 2003-072135 A JP 2001-350111 A

In the conventional method of an optical scanning device using a plurality of light sources such as a surface emitting laser, since one pixel is generally constituted by one light source, there is a problem that variations in the light emission level of each light source directly lead to variations in image density. . In particular, there is no means for correcting pixel variations in the sub-scanning direction in the conventional method.
In addition, when one light source is deteriorated, there is a problem that a light emission level reduction due to the characteristic deterioration directly leads to an image density reduction.

  The present invention enables high-speed and high-accuracy optical scanning with a simple configuration, enables correction of scanning unevenness and scanning width, and can correct the variation even when there is a large variation in linearity. An object is to provide a dot position correction device, an optical scanning device, an image forming device, and a color image forming device.

  In order to achieve the above object, the invention according to claim 1 is the first control data based on the high frequency clock generating means for generating the high frequency clock, the phase data indicating the phase shift amount of the pixel clock, and the state signal indicating the state of the pixel clock. And control data generation means for generating second control data, first clock generation means for generating a first clock based on the high-frequency clock and the first control data, and based on the high-frequency clock and the second control data And a second clock generation unit that generates a second clock; and a clock selection unit that selects one of the first clock and the second clock and outputs the selected clock as a pixel clock. The first clock generation means includes a first detection means for detecting a transition of the first clock, an output of the first detection means, and the first control. First control signal generating means for generating a first control signal based on the data, and causing the signal to transition at the first change point timing of the high-frequency clock based on the first control signal, so that the signal is transferred to the first clock A first signal transition means for outputting as a main scanning dot position correction means for correcting the dot position in the main scanning direction based on the phase shift of the pixel clock of the pixel clock generation section, and a plurality of light emitted from the light source The light source in an optical scanning device that forms an image by scanning a light beam along a scanning direction along a scanning direction with a deflector has a plurality of main light sources, and a plurality of sub-light sources with respect to one main light source. A sub-scanning dot position correcting unit that has a light source and corrects the dot position in the sub-scanning direction by scanning the main light source and the sub-light source on different scanning lines, and the light emission of each light source Timing is generated based on the pixel clock generator.

  According to a second aspect of the present invention, in the dot position correcting apparatus according to the first aspect, the second clock generation unit includes a second detection unit that detects a transition of the second clock, and an output from the second detection unit. And second control signal generating means for generating a second control signal based on the second control data, and causing the signal to transition at the second change point timing of the high-frequency clock based on the second control signal. And a second signal transition means for outputting a signal as a second clock.

  According to a third aspect of the present invention, in the dot position correction apparatus according to the first or second aspect, the light emitted from the main light source and the one or more sub-light sources is scanned by the deflector along the main scanning direction. When scanning on a medium, the main light source constituting one dot for one dot formed by the main light source and the sub light source performing light emission scanning at substantially the same position in the main scanning direction on the scanned medium; The total light emission time of the sub-light source is substantially constant for each dot.

  According to a fourth aspect of the present invention, in the dot position correcting apparatus according to the first or second aspect, the light to be emitted from the main light source and the one or more sub-light sources is scanned along the main scanning direction by the deflector. When scanning on a medium, the main light source constituting one dot for one dot formed by the main light source and the sub light source performing light emission scanning at substantially the same position in the main scanning direction on the scanned medium; The total light emission energy of the sub-light source is substantially constant for each dot.

  According to a fifth aspect of the present invention, in the dot position correction apparatus according to the first or second aspect, the functions of the main light source and the sub light source are switched at a prescribed timing cycle.

  According to a sixth aspect of the present invention, in the dot position correction apparatus according to the first or second aspect, the main scanning dot position deviation amounts of the main light source and the sub light source constituting one pixel are set to substantially the same data.

  According to a seventh aspect of the present invention, in the dot position correcting apparatus according to any one of the first to sixth aspects, the plurality of light sources use surface emitting lasers configured on the same chip.

  According to an eighth aspect of the present invention, in an optical scanning device that forms an image by scanning a plurality of light beams emitted from a light source on a scanned medium along a scanning direction by a deflector, a high frequency that generates a high frequency clock. Clock generation means; control data generation means for generating first control data and second control data from phase data indicating the phase shift amount of the pixel clock and a state signal indicating the state of the pixel clock; the high-frequency clock; First clock generating means for generating a first clock based on the control data; second clock generating means for generating a second clock based on the high frequency clock and the second control data; the first clock and the first clock; A pixel clock generation unit having clock selection means for selecting any one of the two clocks and outputting it as a pixel clock; The first clock generation means is a first detection means for detecting a transition of the first clock, and a first control signal for generating a first control signal based on the output of the first detection means and the first control data. Generating means; and first signal transition means for causing a signal to transition at a first change point timing of the high-frequency clock based on the first control signal and outputting the signal as a first clock. Main scanning dot position correction means for correcting dot position in the main scanning direction based on the phase shift of the pixel clock of the clock generation unit, and the light source has a plurality of main light sources, and a plurality of sub-light sources with respect to one main light source. And a sub-scanning dot position correcting unit that corrects the dot position in the sub-scanning direction by scanning different scanning lines between the main light source and the sub-light source, and the light emission timing of each light source is the pixel clock. It is generated based on the clock generation unit.

  According to a ninth aspect of the present invention, in the optical scanning device according to the eighth aspect, the second clock generation means includes a second detection means for detecting a transition of the second clock, and an output from the second detection means. Second control signal generating means for generating a second control signal based on the second control data, and causing the signal to transition at the second change point timing of the high-frequency clock based on the second control signal. And second signal transition means for outputting as a second clock.

  According to a tenth aspect of the present invention, in the optical scanning device according to the eighth or ninth aspect, the light to be emitted from the main light source and the one or more auxiliary light sources is scanned by the deflector along the main scanning direction. When scanning above, the main light source and the main light source constituting one dot for one dot formed by the main light source and the sub-light source performing light emission scanning at substantially the same position in the main scanning direction on the scanned medium The total light emission time of the sub-light source is substantially constant for each dot.

  The invention according to claim 11 is the optical scanning device according to claim 8 or 9, wherein the light to be emitted from the main light source and the one or more auxiliary light sources is scanned along the main scanning direction by the deflector. When scanning above, the main light source and the main light source constituting one dot for one dot formed by the main light source and the sub-light source performing light emission scanning at substantially the same position in the main scanning direction on the scanned medium The total light emission energy of the sub-light source is substantially constant for each dot.

  According to a twelfth aspect of the present invention, in the optical scanning device according to the eighth or ninth aspect, the functions of the main light source and the sub light source are switched at a prescribed timing cycle.

  According to a thirteenth aspect of the present invention, in the optical scanning device according to the eighth or ninth aspect, the main scanning dot position shift amounts of the main light source and the sub light source constituting one pixel are made substantially the same data.

  According to a fourteenth aspect of the present invention, in the optical scanning device according to any one of the eighth to thirteenth aspects, the plurality of light sources use surface-emitting lasers configured on the same chip.

  An invention according to a fifteenth aspect includes the dot position correcting device according to any one of the first to seventh aspects or the optical scanning device according to any one of the eighth to fourteenth aspects.

  The invention according to claim 16 includes the dot position correcting device according to any one of claims 1 to 7 or the optical scanning device according to any one of claims 8 to 14, and a plurality of color images. Is a color image forming apparatus that forms a color image by superimposing the main scanning dot position correction and the sub scanning dot position correction of each image of another color with reference to the positional deviation amount of the image of a specific color. is there.

  According to a seventeenth aspect of the present invention, there is provided a plurality of image forming means having the dot position correcting device according to any one of the first to seventh aspects or the optical scanning device according to any one of the eighth to fourteenth aspects. In the provided color image forming apparatus, the plurality of light sources use a plurality of surface emitting lasers each having a plurality of lattice-shaped light sources on a chip for each color.

  According to an eighteenth aspect of the present invention, a plurality of image forming means having the dot position correcting device according to any one of the first to seventh aspects or the optical scanning device according to any one of the eighth to fourteenth aspects. A color image forming apparatus comprising: a plurality of scanned media with a light beam deflected by the deflector using light guide means for guiding the light beam deflected by the deflector onto the plurality of scanned media; It is a tandem type that scans the top to form an image.

  According to the present invention, it is possible to perform high-speed and high-accuracy optical scanning with a simple configuration, correction of scanning unevenness and correction of scanning width, and correction of the variation even when there is a large variation in linearity. It becomes possible.

  FIG. 16 shows the configuration of the pixel clock generation circuit in Embodiment 1 of the present invention. In FIG. 16, a pixel clock generation circuit 10 includes a high frequency clock generation circuit 11 as high frequency clock generation means for generating a high frequency clock, and a transition detection circuit as first detection means for detecting a transition of the first clock (clock 1). 12, a control signal generation circuit 13 as a first control signal generation means for generating a first control signal (control signals 1a, 1b) based on the output of the first detection means and the first control data (control data 1); A clock 1 generation circuit 14 serving as a first signal transition means for causing the signal to transition at the first change point timing of the high-frequency clock based on the first control signal and outputting the signal as a first clock; and a second clock A transition detection circuit 15 as second detection means for detecting a transition of the second control signal, and a second control signal (control signal 2a) based on the output from the second detection means and the second control data. 2b), a control signal generation circuit 16 as second control signal generation means, and a signal transition is performed at the second change point timing of the high-frequency clock based on the second control signal, and the signal is transmitted to the second clock. A clock 2 generation circuit 17 as a second signal transition means for outputting as a signal, a multiplexer 18 as a clock selection means for selecting one of the first clock and the second clock and outputting it as a pixel clock, and the phase of the pixel clock Control data as control data generating means for generating first control data (control data 1) and second control data (control data 2) from phase data indicating the shift amount and a status signal (status signal) indicating the state of the pixel clock A generation circuit 19, a status signal generation circuit 20, and a select signal generation circuit 21 are included.

  The transition detection circuit 12 as the first detection means, the control signal generation circuit 13 as the first control signal generation means, and the clock 1 generation circuit 14 as the first signal transition means are based on the high-frequency clock and the first control data. The first clock generating means for generating the first clock is configured. The transition detection circuit 15 as the second detection means, the control signal generation circuit 16 as the second control signal generation means, and the clock 2 generation circuit 17 as the second signal transition means are based on the high frequency clock and the second control data. Second clock generating means for generating the second clock.

  The high frequency clock generation circuit 11 generates a high frequency clock VCLK serving as a reference for the pixel clock PCLK. The transition detection circuit 12 operates at the rising edge of the high frequency clock VCLK from the high frequency clock generation circuit 11, detects the rising edge of the clock 1 from the clock 1 generation circuit 14, and has a pulse of one clock width (one cycle) of the high frequency clock VCLK. The signal is output as detection signal 1. The control signal generation circuit 13 operates at the rising edge of the high frequency clock VCLK, and shifts the phase shift of the pixel clock PCLK in accordance with the output signal of the transition detection circuit 12 and the control data 1 from the control data generation circuit 19 (the rising edge of the high frequency clock VCLK. The control signal 1a and the control signal 1b for shifting the phase of the clock 1 are output on the basis of the control data for execution. The clock 1 generation circuit 14 operates at the rising edge of the high-frequency clock VCLK, and generates the clock 1 according to phase data given from the outside based on the control signal 1a and the control signal 1b from the control signal generation circuit 13.

  The transition detection circuit 15 operates at the falling edge of the high frequency clock VCLK from the high frequency clock generation circuit 11, detects the rising edge of the clock 2 from the clock 2 generation circuit 17, and 1 of the high frequency clock VCLK from the high frequency clock generation circuit 11. A pulse signal with a clock width is output. The control signal generation circuit 16 operates at the falling edge of the high frequency clock VCLK from the high frequency clock generation circuit 11, and the output signal of the transition detection circuit 15 and the control data 2 from the control data generation circuit 19 (at the falling edge of the high frequency clock VCLK). In addition, a control signal 2a and a control signal 2b for shifting the phase of the clock 2 are output based on the control data for performing the phase shift of the pixel clock PCLK. The clock 2 generation circuit 17 operates at the falling edge of the high frequency clock VCLK from the high frequency clock generation circuit 11, and generates the clock 2 based on the control signal 2a and the control signal 2b from the control signal generation circuit 16. The multiplexer 18 selects either the clock 1 from the clock 1 generation circuit 14 or the clock 2 from the clock 2 generation circuit 17 based on the select signal from the select signal generation circuit 21 and outputs it as the pixel clock PCLK.

  As shown in FIG. 17, the control data generation circuit 19 outputs control data 1 and control data 2 based on phase data given from the outside and a status signal output from the status signal generation circuit 20. Here, the phase data corrects the scanning unevenness caused by the characteristics of the scanning lens of the optical scanning device, corrects the dot position shift caused by the rotational unevenness of the polygon mirror of the optical scanning device, or the laser beam of the optical scanning device. This data is used to indicate the shift amount of the phase of the pixel clock in order to correct the dot position shift caused by chromatic aberration. Here, the data has a 3-bit configuration, and the phase shift amount and the phase data correspond to each other as shown in FIG. .

The status signal generation circuit 20 receives the phase data and generates a status signal as a state signal indicating the state of the pixel clock. When the bit 0 of the phase data is 1, as shown in FIG. The signal is toggled at the rising edge of the signal and the signal is output as a status signal. Accordingly, the status signal output from the status signal generation circuit 20 indicates the first state when the pixel clock PCLK rises when the high-frequency clock VCLK rises, and the pixel clock PCLK falls when the high-frequency clock VCLK falls. When it is, the second state is indicated. Here, the status signal is “0” when the pixel clock PCLK rises when the high-frequency clock VCLK rises, and “1” when the pixel clock PCLK falls when the high-frequency clock VCLK falls.
When the phase data is given and bit 0 of the phase data is 1, the select signal generation circuit 21 toggles the signal at the falling timing of the pixel clock PCLK and outputs the signal as a select signal.

  Next, the operation of the pixel clock generation circuit 10 will be described with reference to the timing chart of FIG. In FIG. 18, when the phase shift is 0, the pixel clock PCLK corresponding to the frequency divided by 8 of the high frequency clock VCLK is generated, and the phase is +1/16 (+1/16 cycle), −1/16 (−1 / 16 period) The pixel clock PCLK shifted is shown.

First, generation of a pixel clock PCLK with a phase shift of 0 will be described.
(Regarding generation of control data 1 and control data 2)
The pixel clock generation circuit 10 is supplied with phase data “000” indicating phase shift 0 in synchronization with the pixel clock PCLK (FIG. 18 (1)). The control data generation circuit 19 receives the phase data and the status signal from the status signal generation circuit 20 (initially set to 0), and controls data for controlling the phase shift to 0 according to the truth table of FIG. 1 (010) and control data 2 (010) are output.

(Clock 1 generation)
The transition detection circuit 12 operates at the rising timing (1) of the high frequency VCLK shown in FIG. 18 to detect the rising edge of the clock 1 from the clock 1 generation circuit 14, and as shown in FIG. A pulse signal of 1 clock width of VCLK is output. This detection signal 1 is given to the shift register (1) in the control signal generation circuit 13, and register output signals S10 to S18 as shown in FIG. 18 are obtained. The control signal generation circuit 13 always outputs the register output signal S12 itself as the control signal 1a. This control signal 1a becomes “H” at the rising timing (2) of the high frequency clock VCLK shown in FIG. 18 and becomes “H” at the rising timing (3) of the next high frequency clock VCLK shown in FIG. The clock 1 generation circuit 14 changes the clock 1 to “L” at the rising timing (3) of the high frequency clock VCLK shown in FIG. The control signal generation circuit 13 outputs the register output signal S16 as the control signal 1b because the control data 1 is data “010” in which the phase shift is 0. The control signal 1b becomes “H” at the rising timing (4) of the high frequency clock VCLK shown in FIG. 18, and the control signal 1b becomes “H” at the rising timing (5) of the high frequency clock VCLK shown in FIG. Therefore, the clock 1 generation circuit 14 changes the clock 1 to “H” and outputs it at the rising timing (5) of the high-frequency clock VCLK shown in FIG.

(Clock 2 generation)
The transition detection circuit 15 operates at the falling timing (1) ′ of the high-frequency clock VCLK shown in FIG. 18 to detect the rising edge of the clock 2 from the clock 2 generation circuit 17, and as shown in FIG. 2, a pulse signal having a width of one clock of the high-frequency clock VCLK is output. This detection signal 2 is given to the shift register (2) in the control signal generation circuit 16, and register output signals S20 to S28 as shown in FIG. 18 are obtained. The control signal generation circuit 16 outputs the register output signal S22 itself as the control signal 2a. The control signal 2a becomes “H” at the timing (2) ′ of the falling edge of the high-frequency clock VCLK shown in FIG. 18 and “H” at the next falling timing (3) ′ of the high-frequency clock VCLK shown in FIG. Since it is “H”, the clock 2 generation circuit 17 shifts the clock 2 to “L” at the timing (3) ′ and outputs it. The control signal generation circuit 16 outputs the register output signal S26 as the control signal 2b because the control data 2 is data “010” whose phase shift is 0. The control signal 2b becomes “H” at the falling timing (4) ′ of the high frequency clock VCLK shown in FIG. 18, and becomes “H” at the falling timing (5) ′ of the high frequency clock VCLK shown in FIG. Therefore, the clock 2 generation circuit 17 shifts the clock 2 to “H” at the timing (5) ′ and outputs it.

(Regarding generation of pixel clock PCLK)
Here, since the select signal from the select signal generation circuit 21 is “L”, the multiplexer 18 selects and outputs the clock 1 from the clock 1 generation circuit 14 as the pixel clock PCLK.

Next, generation of the pixel clock PCLK whose phase is shifted by +1/16 (+1/16 period) will be described.
(Regarding generation of control data 1 and control data 2)
The pixel clock generation circuit 10 is given phase data “001” indicating a phase shift + 1/16 in synchronization with the pixel clock PCLK (FIG. 18 (5)). The status signal output from the status signal generation circuit 20 remains “0” without being toggled because bit0 of the previous phase data is “0”. The control data generation circuit 19 receives the phase data and the status signal from the status signal generation circuit 20, and in accordance with the truth table of FIG. 17, the control data 1 (010) for setting the phase shift to 0 and the phase shift for + 1 / 16 is output as control data 2 (001).

(Clock 1 generation)
The transition detection circuit 12 operates at the rising timing (5) of the high-frequency clock VCLK shown in FIG. 18 to detect the rising edge of the clock 1 from the clock 1 generation circuit 14, and as shown in FIG. A pulse signal having a width of one clock of the high-frequency clock VCLK is output. This detection signal 1 is given to the shift register (1) in the control signal generation circuit 13, and register output signals S10 to S18 as shown in FIG. 18 are obtained. The control signal generation circuit 13 outputs the register output signal S12 itself as the control signal 1a. This control signal 1a becomes “H” at the rising timing (6) of the high frequency clock VCLK shown in FIG. 18, and becomes “H” at the next rising timing (7) of the high frequency clock VCLK shown in FIG. The clock 1 generation circuit 14 changes the clock 1 to “L” at the timing (7) and outputs it. The control signal generation circuit 13 outputs the register output signal S16 as the control signal 1b because the control data 1 is “010” with a phase shift of 0. The clock 1 generation circuit 14 becomes “H” at the rising timing (8) of the high frequency clock VCLK shown in FIG. 18, and becomes “H” at the next rising timing (9) of the high frequency clock VCLK shown in FIG. Then, the clock 1 is shifted to “H” at the timing (9) and output.

(Clock 2 generation)
The transition detection circuit 15 detects the rising edge of the clock 2 from the clock 2 generation circuit 17 at the falling timing (5) ′ of the high-frequency clock VCLK shown in FIG. 18 and, as shown in FIG. A pulse signal having a clock width of one clock VCLK is output. This detection signal 2 is given to the shift register (2) in the control signal generation circuit 16, and register output signals S20 to S28 as shown in FIG. 18 are obtained. The control signal generation circuit 16 always outputs the register output signal S22 itself as the control signal 2a. The control signal 2a becomes “H” at the falling timing (6) ′ of the high frequency clock VCLK shown in FIG. 18, and “H” at the next falling timing (7) ′ of the high frequency clock VCLK shown in FIG. Therefore, the clock 2 generation circuit 17 changes the clock 2 to “L” and outputs it. Then, since the control data 2 is “001” in which the control data 2 has a phase shift of +1/16, the control signal generation circuit 16 uses the control signal 2b as the control signal 2b so that the phase is +1 stage (one clock width of the high-frequency clock VCLK). The shifted register output signal S27 is output. The control signal 2b becomes “H” at the falling timing (8) ′ of the high frequency clock VCLK shown in FIG. 18, and “H” at the next falling timing (9) ′ of the high frequency clock VCLK shown in FIG. Therefore, the clock 2 generation circuit 17 shifts the clock 2 to “H” at the timing (9) ′ and outputs it.

(Regarding generation of pixel clock PCLK)
Here, since the bit 0 of the phase data is “1”, the select signal generation circuit 21 outputs the select signal at the falling timing of the pixel clock PCLK that is the rising timing (7) of the high-frequency clock VCLK shown in FIG. Toggle to “1”. Therefore, the multiplexer 18 starts with the select signal from the select signal generation circuit 21 at the beginning (period (5) to (7) of the rising edge of the high frequency clock VCLK shown in FIG. 18). Is selected and output as the pixel clock PCLK, and the select signal becomes “1” at the rising timing (7) of the high frequency clock VCLK shown in FIG. 18 (the rising timing of the high frequency clock VCLK shown in FIG. 18 ( 7) to (9) ′), the clock 2 from the clock 2 generation circuit 17 is output as the pixel clock PCLK.

Next, generation of the pixel clock PCLK for shifting the phase by −1/16 will be described.
(Regarding generation of control data 1 and control data 2)
In synchronization with the pixel clock PCLK, the pixel clock generation circuit 10 is provided with phase data “111” indicating phase shift−1 / 16 at the falling timing (9) ′ of the high-frequency clock VCLK shown in FIG. The status signal output from the status signal generation circuit 20 is toggled to “1” because bit 0 of the previous phase data is “1” (the falling timing of the high-frequency clock VCLK shown in FIG. 18 (9 ) ´). The control data generation circuit 19 receives the phase data and the status signal from the status signal generation circuit 20, and in accordance with the truth table of FIG. 17, the control data 1 (010) for setting the phase shift to 0 and the phase shift of −1. Control data 2 (011) to be set to / 16 is output.

(Clock 1 generation)
The transition detection circuit 12 operates at the rise timing (9) of the high-frequency clock VCLK shown in FIG. 18 to detect the rise of the clock 1 from the clock 1 generation circuit 14, and as shown in FIG. A pulse signal having a width of one clock of the high-frequency clock VCLK is output. This detection signal 1 is given to the shift register (1) in the control signal generation circuit 13, and register output signals S10 to S18 as shown in FIG. 18 are obtained. The control signal generation circuit 13 outputs the register output signal S12 itself as the control signal 1a. The control signal 1a becomes “H” at the timing (10) of the rising edge of the high frequency clock VCLK shown in FIG. 18, and becomes “H” at the timing (11) of the next rising edge of the high frequency clock VCLK shown in FIG. Therefore, the clock 1 generation circuit 14 changes the clock 1 to “L” and outputs it. The control signal generation circuit 13 outputs the register output signal S16 as the control signal 1b because the control data 1 is “010” with a phase shift of 0. This control signal 1b becomes “H” at the rising timing (12) of the high frequency clock VCLK shown in FIG. 18, and becomes “H” at the next rising timing (13) of the high frequency clock VCLK shown in FIG. The clock 1 generation circuit 14 shifts the clock 1 to “H” and outputs it.

(Clock 2 generation)
The transition detection circuit 15 operates at the falling timing (9) ′ of the high-frequency clock VCLK shown in FIG. 18 to detect the rising edge of the clock 2 from the clock 2 generation circuit 17, and as shown in FIG. 2, a pulse signal having a width of one clock of the high-frequency clock CLK is output. This detection signal 2 is given to the shift register (2) in the control signal generation circuit 16, and register output signals S20 to S28 as shown in FIG. 18 are obtained. The control signal generation circuit 16 outputs the register output signal S22 itself as the control signal 2a. The control signal 2a becomes “H” at the falling timing (10) ′ of the high frequency clock VCLK shown in FIG. 18, and becomes “H” at the next falling timing (11) ′ of the high frequency VCLK shown in FIG. Therefore, the clock 2 generation circuit 17 shifts the clock 2 to “L” and outputs it. Then, since the control data 2 is “011” in which the control data 2 has a phase shift of −1/16, the control signal generation circuit 16 has a phase −1 step (one clock width of the high frequency VCLK) as the control signal 2b from the register output signal S26. ) The shifted register output signal S25 is output. The control signal 2b becomes “H” at the falling timing (12) ′ of the high frequency clock VCLK shown in FIG. 18, and “H” at the next falling timing (13) ′ of the high frequency clock VCLK shown in FIG. Therefore, the clock 2 generation circuit 17 changes the clock 2 to “H” and outputs it.

(Regarding generation of pixel clock PCLK)
Here, since the bit 0 of the phase data is “1”, the select signal generation circuit 21 uses the select signal as the falling timing of the pixel clock PCLK (the falling timing (11) ′ of the high frequency VCLK shown in FIG. 18). Toggle to “0”. Therefore, the multiplexer 18 selects the clock 2 from the clock 2 generation circuit 17 as the pixel clock PCLK at the beginning (period of the falling timing (9) ′ to (11) ′ of the high frequency clock VCLK shown in FIG. 18). 18 and the select signal becomes “0” at the falling timing (11) ′ of the high frequency clock VCLK shown in FIG. 18 (from the falling timing (11) ′ of the high frequency clock VCLK shown in FIG. 18, the clock 1 from the clock 1 generation circuit 14 is selected and output as the pixel clock PCLK.

In the above operation, only the phase shifts 0, +1/16, and −1/16 of the pixel clock PCLK have been described, but the phase shifts +2/16, +3/16, −2/16, and −3/16 of the pixel clock PCLK are described. Can be done in the same way.
By doing as described above, it is possible to obtain the pixel clock PCLK whose phase is shifted by ± 1/16 step by one clock, that is, by a half pitch step of the high frequency clock VCLK.

  In FIG. 16, if a clock obtained by inverting the high-frequency clock VCLK is given to the transition detection circuit 15, the control signal generation circuit 16, and the clock 2 generation circuit 17, the transition detection circuit 15, the control signal generation circuit 16, The clock 2 generation circuit 17 can be composed of the same components as the transition detection circuit 12, the control signal generation circuit 13, and the clock 2 generation circuit 14, and the cost is reduced.

FIG. 21 shows the overall configuration of the optical scanning device according to the first embodiment.
A plurality of laser beams from a semiconductor laser unit 201 using a surface emitting laser as a light source device pass through a collimator lens 202 and a cylinder lens 203 and are scanned (scanned) by a polygon mirror 204 as a deflector. As a result, the light is reflected by the mirror 208, passes through the toroidal lens 206, and is incident on the photosensitive member 208 as a medium to be scanned, so that the photosensitive member 208 is scanned and exposed in the main scanning direction. The photosensitive member 208 is rotationally driven by a driving unit (not shown) and is uniformly charged by a charging device (not shown), and then an electrostatic latent image is formed by exposure with the laser beam, and is developed by a developing device (not shown) to be a toner image. Is formed. The toner image on the photoconductor 208 is transferred onto a transfer sheet by a transfer device (not shown), and the toner image is fixed to the transfer paper by a fixing device (not shown) and discharged to the outside.

  Scanning laser light from the fθ lens 205 is detected by photosensors 101 and 102 serving as photodetectors at the start and end points in the main scanning direction (front and rear sides of the image forming area of the photoconductor 208). The output signal 102 is input to the dot position deviation detection / control unit 110. The dot position deviation detection / control unit 110 measures the time during which the laser beam scans between the photosensors 101 and 102 from the output signals of the photosensors 101 and 102, and compares the time with the reference time to perform main scanning. A direction dot position deviation amount is obtained, phase data for correcting the deviation amount is generated, and output to the pixel clock generation unit 10. Note that the output signal of the photosensor 101 is also provided to the image processing unit 130 as a line synchronization signal.

  If the pixel clock generation unit 10 does not include a phase data storage circuit that stores phase data, the dot position deviation detection / control unit 110 outputs phase data to the pixel clock generation unit 10 for each line. However, when the phase data storage circuit is provided, the phase data is obtained in advance and stored in the pixel clock generation unit 10 by obtaining the phase data in advance. Further, the dot position deviation detection / control unit 110 uses only phase data (first phase data) for always performing the same correction for each line so as to correct the dot position deviation due to the scanning unevenness caused by the characteristics of the scanning lens 205. In addition, phase data (second phase data) or the like is also generated for coping with correction of dot position deviation that changes for each line such as uneven rotation of the polygon mirror 204, and the pixel clock generation unit 10 generates a phase data synthesis circuit. Are provided to the pixel clock generator 10 to be synthesized by the phase data synthesis circuit. Further, when a multi-beam scanning device is used, it is possible to simultaneously generate phase data for a plurality of lines by providing a plurality of sets of photosensors 101 and 102. Here, the dot position deviation detection / control unit 110 and the pixel clock generation unit 10 constitute main scanning dot position correction means.

  The pixel clock generation unit 10 generates a pixel clock based on the phase data from the dot position deviation detection / control unit 110, and provides this pixel clock to the image processing unit 130 and the laser drive data generation unit 140. The image processing unit 130 generates image data based on the pixel clock from the pixel clock generation unit 10 and outputs the image data to the laser drive data generation unit 140. The laser drive data generation unit 140 generates laser drive data (modulation data) based on the image data from the image processing unit 130 based on the pixel clock from the pixel clock generation unit 10, and the laser drive data (modulation data) is laser-generated. Output to the drive unit 150. The laser driving unit 150 drives each light source of the semiconductor laser unit 201 based on the laser driving data (modulation data) from the laser driving data generation unit 140. As a result, an image having no dot position deviation can be formed on the photoreceptor 208.

  FIG. 22 shows an example of a pulse generated by a pulse width modulation circuit provided in the laser drive data generation unit 140 as image data and a dot image when, for example, one dot is composed of eight pulses. FIG. FIG. 22 shows an example in which a pulse is formed from the center of one dot. Here, the dot image indicates the width of one dot, the image data 1 is 1/8 width of the dot image, the image data 2 is 2/8 of the dot image,..., And the image data 8 is 8/8 of the dot image. In this way, it is assumed that the image data is defined by the time width. FIG. 23 is a table showing patterns for giving image data to the light sources A, B, and C in FIG. 4 using the pulse width modulation circuit having the relationship between the image data and dot image output of FIG. The vertical axis of this table indicates 16 types of data patterns given to the light source composed of the light sources A, B, and C constituting one pixel, and the numbers of the light sources A, B, and C indicate image data. By changing the data pattern according to the amount of sub-scanning dot position deviation of the pixel, it becomes possible to shift the center of gravity position of the scanning light quantity distribution in the sub-scanning direction as shown in FIG. 4 and correct the amount of sub-scanning dot position deviation. By giving a data pattern as described above, sub-scanning dot position deviation correction can be performed.

FIG. 24 shows an example of a pulse modulation signal generation circuit according to the first embodiment.
The pulse modulation signal generation circuit 500 is a pulse width modulation signal generation circuit including a high frequency clock generation circuit 501, a modulation data generation circuit 502, and a serial modulation signal generation circuit 503. The high-frequency clock generation circuit 501 generates a high-frequency clock VCLK that is much faster than a basic cycle that represents one dot, which is generally called a pixel clock required by an image forming apparatus.

  The modulation data generation circuit 502 generates modulation data representing a desired bit pattern based on image data given from the outside such as the image processing unit 130 (not shown). The serial modulation signal generation circuit 503 receives the modulation data output from the modulation data generation circuit 502 and converts it into a serial pulse pattern sequence (pulse sequence) based on the high frequency clock VCLK from the high frequency clock generation circuit 501. And output as a pulse modulation signal PWM. For example, if modulation data from the outside is directly input to the serial modulation signal generation circuit 503, the modulation data generation circuit 502 can be omitted.

  The greatest feature of the pulse modulation signal generation circuit 500 is that modulated data is input to the serial modulation signal generation circuit 503, and this is converted into a pulse train corresponding to the bit pattern of the modulation data based on a high-frequency clock much faster than the pixel clock. To generate a pulse modulation signal PWM. For example, a shift register may be used for the serial modulation signal generation circuit 503.

  Further, by storing the data pattern shown in FIG. 23 in a lookup table or the like and using it as the serial modulation signal generation circuit 503, when the data pattern is, for example, the data pattern 6, the image data 5 is the image data for the light source B. The image data 3 is input to the pulse modulation signal generation circuit 500 as the image data for the light source C, and the pulse pattern is output as a dot image shown in FIG.

  Here, consider the case where the light emission amount control of the light sources A, B, and C is performed with reference to FIG. In FIG. 23, assuming that the numbers of the light sources A, B, and C are the light emission levels with respect to the data pattern, the maximum light emission amount of the light sources A, B, and C is 8. At this time, all the data patterns are defined and set so that the sum of the light emission levels of the light sources A, B, and C is 8. In FIG. 5, by controlling the light emission levels of the light sources A, B, and C with the data pattern shown in FIG. 23, the light quantity ratios of the light sources A, B, and C can be set with a simple configuration. Because of the difference in the amount of light emitted from these three light sources A, B, and C, the barycentric position of the scanning light amount distribution can be shifted in the sub-scanning direction in which the light sources A, B, and C are arranged. By changing the light emission patterns of the light sources A, B, and C according to the above, sub-scanning dot position deviation correction can be performed.

  FIG. 25 shows another example of the pulse modulation signal generation circuit 500 provided in the laser drive data generation unit 140 in the first embodiment. The pulse modulation signal generation circuit 500 includes a power modulation signal generation circuit. In the pulse modulation signal generation circuit 500, the image data input to the modulation data generation circuit 502 indicates the light emission amounts of the light sources A, B, and C, and is intensity-modulated by the modulation data generation circuit 502. The modulation data from the modulation data generation circuit 502 is based on a high-frequency clock that is much faster than the pixel clock generated by the high-frequency clock generation circuit 501 in the serial modulation signal generation circuit 504, and the power corresponding to the emission intensity of the modulation data. The signal is serially output as a power modulation signal PM. The feature of the first embodiment is that dot position deviation correction in the sub-scanning direction is performed by setting the light emission powers of the light sources A, B, and C according to the values of the image data in each data pattern of FIG. The serial modulation signal generation circuit 503 or 504 constitutes a sub-scanning dot position correction unit that performs dot position correction in the sub-scanning direction.

FIG. 1 shows a light source of the first embodiment.
As shown in FIG. 1, the light source device 201 includes a plurality of laser elements P1A, P1B, P1C, P2A, P2B, P2C,... P4A, P4B, and P4C arranged in a grid in the x and y directions perpendicular to each other. Or a plurality of laser elements P1A, P1B, P1C, P2A, P2B, P2C,... P4A, P4B, and P4C as a plurality of light sources on the same chip. Adjusts the arrangement and angle of the light sources P1A to P4C so that they have a predetermined angle θ with respect to the deflector 204. In FIG. 1, when one pixel is composed of the light sources P1A and P2A, the light source P2A is a light source that forms a main pixel, and the light sources P1A and P3A are light sources that form sub-pixels. Similarly, light sources P2B, P2C, P4A, P4B, and P4C are light sources that form main pixels, and light sources P1B, P1C, P3B, and P3C are light sources that form sub-pixels.

4 and 5 are schematic diagrams of dot position correction in the main scanning direction and the sub-scanning direction depending on how data of the main pixel and sub-pixel are given.
FIG. 4 shows the light emission signals of the light sources A, B, and C in the upper part of FIG. 4, and the lower part of FIG. The image figure of the scanning light quantity at the time of scanning in the scanning direction is shown. For example, consider the case where the light source P2A in FIG. 1 is the light source B in FIG. 4, the light source P1A is the light source A, and the light source P3A is the light source C. At this time, assuming that the light source B (light source P2A) is the main pixel, the state of the pixel 5 is the reference pixel 2, and the pixel at the position in the main scanning direction does not require position correction in the sub-scanning direction.

  On the other hand, consider the case of pixel 1 and pixel 10, for example. In the pixel 1, only the light source C emits light, and in the pixel 10, only the light source A emits light. When compared with the pixel 5, the pixel 1 has a dot position in the sub-scanning direction when the sub-scanning direction is the lower side in the figure. The pixel position of the pixel 10 is shifted in the direction opposite to the sub-scanning, and the amount of the shift is determined by the scanning interval of the light sources A, B, and C on the scanned medium 208. For example, when the image data is given by the data pattern shown in FIG. 23, the light quantity control can be performed for each light source in FIG. 4 by giving the image data pattern shown in FIG.

When viewed from the pixel 1 to the pixel 5 in order, the light emission time tc of the light source C gradually decreases, and the light emission time tb of the light source B gradually increases. At this time, the center of gravity of the image formed by both light sources B and C approaches the position of the main light source that is the light source B. Similarly, when looking at the pixel 5 and the pixels 7 to 10 in order, the light emission time tb of the light source B gradually decreases and the light emission time tc of the light source A increases.
By adjusting the light emission times of the three light sources A, B, and C in this way, a shift in the center of gravity of the image occurs, and the shift in the center of gravity is recognized as a dot position shift in the sub-scanning direction in the optical scanning device or the image forming apparatus. Therefore, the dot position deviation in the sub-scanning direction can be corrected by controlling the light emission time of each light source according to the first embodiment.

  Consider a case where the total light emission times of the light sources A, B, and C constituting one pixel are substantially the same (or the same). For example, the total light emission time of each light source A, B, and C is controlled by setting the total light emission time of light sources A, B, and C to be equal to ta + tb + tc, thereby correcting the position in the sub-scanning direction. This is substantially the same (or the same) when the position correction in the sub-scanning direction is not performed, so that highly accurate dot position correction in the sub-scanning direction is possible with a simple configuration and control method. For example, in pixel 3, tall3 = tb3 + tc3, in pixel 5, tall5 = tb5, and the relationship of tall3 = tall5 = talln (n is a natural number) is satisfied.

Further, in FIG. 4, the reference pixel 2 is composed of only the pixel 5, that is, the light source B. However, in order to cause a positional shift in the sub scanning direction, the sub light sources A and C need to emit light. In order to improve the gradation with respect to the positional shift caused by the light emission of the light source, the light sources A and C are equivalent to the light amount as in the pixel 6, but compared with the light source B even when the dot position correction in the sub-scanning direction is not necessary. In other words, a method for producing a small light emission can be considered.
In the first embodiment, the dot position correction in the main scanning direction and the sub-scanning direction can be performed by combining the dot position deviation correction in the main scanning direction.

  FIG. 28 shows each pixel in the second embodiment of the present invention when the vertical direction of FIG. 28 is the sub-scanning direction and the horizontal direction is the main scanning direction, and 3 lines are formed in the sub-scanning direction and 10 pixels are formed in the main scanning direction. The control data of the main scanning dot position shift given to FIG. Each of the three lines in the sub-scanning direction has a main light source at the center in the sub-scanning direction and sub-light sources above and below it, and one pixel is formed by superimposing the three light sources in the sub-scanning direction. .

  In FIG. 28, the control data of the main scanning dot position deviation indicates the phase data of FIG. 17, and the phase shift amount is 0 when the phase data is 000, and the phase shift amount is +1 when the phase data is 001. Yes, it is assumed that the phase shift amount is -1 for the phase data 111. At this time, when considering each line, if the main scanning dot position shift amount of the main light source and the sub light source forming the same pixel is changed, a position shift in the main scanning direction occurs in the same pixel, resulting in image deterioration. Connected. Therefore, it is desirable that the main light source and the sub light source in the same line give the same phase data as shown in FIG. 28 for the same pixel.

FIG. 5 shows combinations of light emission amounts for the respective pixels of the light sources A, B, and C when the right direction in the figure is the main scanning direction.
In FIG. 4, the total light emission times of the light sources constituting one pixel are substantially the same (or the same), but the case where the total light emission amounts of the light sources constituting one pixel are substantially the same (or the same) is considered. When the total light emission amount of the light sources A, B, and C is pall, pall4 = pb4 + pc4 in the pixel 4, and pall = pa6 + pb6 + pc6 in the pixel 6. Here, pb4 is the light emission amount at the pixel 4 of the light source B, pc4 is the light emission amount at the pixel 4 of the light source C, pa6 is the light emission amount at the pixel 6 of the light source A, and pb6 is the light emission amount at the pixel 6 of the light source B. , Pc6 is the amount of light emitted from the pixel 6 of the light source C.

  Originally, for example, when a semiconductor laser is used as a light source, when the scanning medium is scanned with a light beam from the light source, the light emission amount of the light source is close to a Gaussian distribution. FIG. 5 schematically shows the total light emission amount per pixel. In the second embodiment, when the actual correction is performed in the first embodiment, the total light amount of the plurality of patterns by the plurality of light sources A, B, and C is fixed in advance on the scanned medium, and the center of gravity is set in the sub-scanning direction. A deviation emission control signal is obtained from the measured value, and a pulse pattern sequence or a power signal corresponding to the emission intensity of the modulation data is serially output by the serial modulation signal generation circuit 503 or 504 based on the measured value. By controlling the light emission amount of the light source, dot position correction in the sub-scanning direction can be performed with high accuracy. For example, when image data is given by the data pattern shown in FIG. 23, it is possible to perform light amount control for each light source in the figure by giving the image data pattern shown in FIG.

  FIG. 2 shows a surface emitting laser as a light source device according to a third embodiment of the invention. In the third embodiment, in the first or second embodiment, two subpixels are formed in both the sub-scanning direction and the opposite direction to the main pixel, and one main pixel and two subpixels are combined. This is an embodiment with one pixel. In the third embodiment, the superposed light (one main pixel and two sub-pixels on both sides thereof) by the optical scanning device can be obtained regardless of whether the scanning position shift in the sub-scanning direction occurs in any direction of the main pixel. It is possible to shift the center of gravity of the scanning light of the pixels, and it is possible to correct the positional deviation in the sub-scanning direction with higher accuracy for all the pixels.

  Conventionally, in order to perform scanning position correction in the sub-scanning direction, a line buffer for storing correction data in advance is necessary, or the influence of pixel data in different line scans is reflected. Some pixel data conversion was necessary. In the third embodiment, the serial modulation signal generation circuit 503 or 504 changes the amount of light from the sub-light source to ½ or less of the amount of light from the main light source, and changes only the amount of light from the sub-light source without changing the amount of light from the main light source. Accordingly, it is possible to configure dot position deviation correction in the sub-scanning direction in a form in which the buffer amount is reduced without data conversion.

  Further, in Embodiment 1 in which the light source device is shown in FIG. 1, it is considered that the main light source and the light source emit light for a longer time than the sub light source in terms of light emission amount and light emission time. Therefore, the lifetime of the main light source is considered to be shorter than that of the sub-light source, and the lifetime of the optical scanning device is shortened as it is. Therefore, in Embodiment 1 described above, the function of the main light source and the sub light source is changed every certain timing cycle such as every line scan or every page scan, thereby preventing deterioration of the light source. The life difference between the main and sub light sources can be reduced, and the life of the entire apparatus can be extended. Similarly, in the second and third embodiments, the roles of the main light source and the sub light source are changed every predetermined time (every specific timing period such as every one line scan or every one page scan). Long life can be expected.

  In the third embodiment, when the interval between the main light sources is Δx, the interval between the main light sources P3A, P2B, P1C, P4C and the auxiliary light sources P2A, P4A, P1B, P3B, P4B, P2C, P3C is Δx / 2. To do. At this time, the sub-light source is disposed near the main light source, and the interval between the sub-light sources is widened, so that overlapping of pixels in the sub-scanning direction can be prevented, and high-precision optical scanning and positional deviation correction are possible. .

  FIG. 3 shows a surface emitting laser as a light source device according to Embodiment 4 of the present invention. The fourth embodiment is the same as the first embodiment or the second embodiment, but the surface emitting laser as the light source device 201 is composed of a plurality of light sources arranged in a grid pattern or a plurality of light sources arranged on the same chip as shown in FIG. The angle of the arrangement of the light sources is adjusted so that the grating has a predetermined angle θ with respect to the deflector 204. At this time, for example, it is assumed that the light source P1A is the main light source 1 and the light source P2A is the main light source 2 to form one pixel with two main light sources. The other light sources P3A and P4A, light sources P1B and P2B, light sources P3B and P4B, light sources P1C and P2C, and light sources P3C and P4C are also two main light sources that form one pixel. When the light emission times or light amounts of the two main light sources forming one pixel are substantially the same (or the same), the center of both light sources becomes the reference pixel position, and the serial modulation signal generation circuit 503 or 504 By providing the difference in the light emission time and light quantity, it becomes possible to shift the center of gravity of the pixel, to realize the positional deviation correction in the sub scanning direction, and to perform the positional deviation correction in the sub scanning direction with high accuracy for each pixel. Become.

  FIG. 6 is a schematic diagram of dot position deviation correction in the sub-scanning direction according to the fourth embodiment. FIG. 6 shows a schematic diagram of dot position correction in the sub-scanning direction using two main light sources forming one pixel in the fourth embodiment as shown in FIG. 3, and the upper part of FIG. The light emission signal is shown. The middle part of FIG. 6 shows the scanning light amount distribution at the time of dot position correction in the sub-scanning direction. The lower part of FIG. 6 shows the dot position in the sub-scanning direction before and after the dot position correction. Shown on the axis. Consider the case where there is a positive or negative positional shift with respect to the scanning position in the sub-scanning direction as shown in the lower data of FIG. 6 (pixel displacement amount in the sub-scanning direction). Note that the pixel position shift amount in the sub-scanning direction is negative in the sub-scanning direction and positive in the direction opposite to the sub-scanning. At this time, since the pixel 1 has a positive displacement with respect to the normal scanning position, the serial modulation signal generation circuit 503 or 504 causes the center of gravity of the pixel to be displaced in the sub-scanning direction as indicated by the scanning light amount distribution. By controlling the amount of light and the light emission time of the two light sources that form one pixel at the same time, the corrected dot position can be corrected to the original position. Similarly, in the case of the pixel 6, there is a negative pixel position misalignment in the sub-scanning direction. At this time, the amount of light of the main pixel 1 or the light emission time is changed by the serial modulation signal generation circuit 503 or 504. By setting it longer than the light emission time, it is possible to correct the displacement in the sub-scanning direction. However, in the configuration of the fourth embodiment, the position when only one of the two light sources forming one pixel is turned on is the maximum position correction amount in the sub-scanning direction.

  FIG. 9 shows a light source device 201 according to the fifth embodiment of the present invention. In the fifth embodiment, in the first embodiment or the second embodiment, the light source device 201 includes two light source devices 201a and 201b. These light source devices 201a and 201b have laser elements P1A, P1B, P1C, P2A, P2B, and P2C as a plurality of light sources arranged in a grid in the x and y directions perpendicular to each other, or as a plurality of light sources on the same chip. Laser elements P1A, P1B, P1C, P2A, P2B, and P2C, and laser elements P3A, P3B, P3C, P4A, and P4B serving as a plurality of light sources in a lattice shape in the x and y directions perpendicular to each other , P4C or a surface emitting laser in which laser elements P3A, P3B, P3C, P4A, P4B, and P4C as a plurality of light sources are arranged on the same chip, and the light sources P1A to P2C and P3A to P4C are arranged. The arrangement and angle of the light sources P1A to P2C and P3A to P4C are adjusted so that the direction has a predetermined angle θ with respect to the deflector 204. To. One of the surface emitting lasers 201a and 201b emits light as a main light source, and the other light source is controlled to emit light. At this time, similarly to the above, the functions of the main light source and the sub light source are changed by the serial modulation signal generation circuit 503 or 504 at every specific timing period such as every line scan or every page scan. Longer service life can be realized. In this way, the life of the light source can be expected to be extended by changing the roles of the main light source and the sub light source with time.

  FIG. 26 shows an example of means for switching the functions of the main light source and the sub light source in the fifth embodiment. For example, when the input data from the serial modulation signal generation circuit 503 or 504 is output to the light sources s1 to s8 (for example, P1A, P1B, P2A, P2B, P3A, P3B, P4A, P4B) through the shift register 505, the reference data. State. Consider a case where shift data is used as a control signal for shifting the state of the input / output signal of the shift register 505 bit by bit from this reference data state. At this time, a counter for counting shift data is provided, and the timing control unit controls the timing of the shift register 505 according to the shift data count value of the counter. FIG. 27 shows the relationship between the shift data and the input / output signals of the shift register 505. The timing control unit sets the shift register 505 to the reference data state when the shift data is 00 or 10, and shifts the input / output signal state of the shift register 505 by 1 bit when the shift data is 01 or 11, thereby shifting the data in the shift register 505. Shift the input / output relationship one bit at a time.

  The light sources s1 to s8 are usually defined as a spare light source (hereinafter also referred to as “preliminary”), a main light source (hereinafter also referred to as “main”), and a secondary light source (hereinafter also referred to as “secondary”) that are not controlled to emit light. For example, under certain conditions, when the light sources s1 to s8 are the pre-sub main sub auxiliary sub auxiliary sub, and the shift data 01 is input to the shift register 505, the roles of the light sources s1 to s8 are Thus, the roles of the light sources s1 to s8 can be switched.

Next, embodiments in which the present invention is applied to an optical scanning device, an image forming apparatus, and a color image forming apparatus will be described.
FIG. 10 shows an example of an optical scanning device used in each of the above embodiments.
In this optical scanning device, in the optical scanning device used in each of the above embodiments, the printed circuit board 802 on which the drive circuit 150 that controls the semiconductor laser and the pixel clock generation unit 10 are formed is formed on the back surface of the light source device 201. The printed circuit board 802 is attached to the wall surface of the optical housing orthogonal to the optical axis by a spring, and the inclination is adjusted by the adjusting screw 803 to maintain the posture. The adjusting screw 803 is screwed into a protrusion formed on the wall surface of the housing. Inside the optical housing, a cylinder lens 203, a polygon motor that rotates the polygon mirror 204, an fθ lens 205, a toroidal lens, and a folding mirror 207 are positioned and supported, and a printed circuit board on which the photosensors 101 and 102 are mounted. Similar to the light source device 201, 809 is attached to the housing wall surface from the outside. The upper portion of the optical housing is sealed with a cover 811 and fixed to the frame member of the image forming apparatus main body with screws by a plurality of mounting portions 810 protruding from the wall surface 804.

Next, an example of a multi-beam scanning device (multi-beam optical system) configured using a plurality of light sources in each of the above embodiments will be described.
FIG. 11 shows an example of a multi-beam scanning device used in the above embodiments. In this multi-beam scanning device, in the multi-beam scanning device used in each of the above embodiments, as the light source device 201, two semiconductor laser arrays 301 in which two light sources are monolithically arranged at a distance ds = 25 μm, 302 is used.

In FIG. 11, the semiconductor laser arrays 301 and 302 are arranged so that the optical axes of the collimating lenses 303 and 304 coincide with each other, have an emission angle symmetrical in the main scanning direction, and the emission axes intersect at the reflection point of the polygon mirror 307. Has been. A plurality of beams emitted from the respective semiconductor laser arrays 301 and 302 are collectively scanned by a polygon mirror 307 through a cylinder lens 308, and are scanned on a photoconductor 208 as a scanning medium through an fθ lens 310 and a toroidal lens 311. Imaged. Print data for one line is stored in the buffer memory 314 in the image forming apparatus for each light source, and is read out for each surface of the polygon mirror 307, and the photosensors 101 and 102, the dot position deviation detection / control unit. 110, the pixel clock generation unit 10, the image processing unit 130, and the laser drive data generation unit 140. The laser drive unit 316 receives the laser drive data (modulation data) from the write control unit 315. The semiconductor laser arrays 301 and 302 are driven, and recording is performed simultaneously every four lines. Further, in order to correct the optical scanning length difference and magnification difference caused by the wavelength error of each of the multi-beams from the semiconductor laser arrays 301 and 302, the pixel clock phase shift in the pixel clock generation unit 10 is corrected. By performing the above, it is possible to correct the difference in the scanning length to the accuracy of the phase shift and reduce the variation in the scanning light.
12A and 12B are exploded perspective views showing a part of another example of the optical scanning device having a laser array in which the vertical direction in the drawing is the sub-scanning direction of the optical system and the light sources are arranged in the sub-scanning direction. It is a figure and a perspective view. In this optical scanning device, in the optical scanning device of the first embodiment, the light source device 201 uses a laser array 506 having four light sources in the vertical direction.
FIGS. 13A and 13B show part of an example of a scanning apparatus having a surface emitting laser 507 in which a plurality of light sources are arranged on a plane. In this optical scanning device, in the optical scanning device of the first embodiment, a plurality of light sources are arranged in a lattice pattern, three light sources are arranged in the horizontal direction, and four light sources are arranged in the vertical direction. Thus, a surface emitting laser 507 having a total of 12 light sources is used.

FIG. 14 shows another embodiment 6 of the image forming apparatus to which the present invention is applied. In the sixth embodiment, a charging charger 902 for charging the photosensitive member 901 to a high voltage and a static electricity recorded on the photosensitive member 901 by exposure by the optical scanning device 900 are provided around the photosensitive drum 901 as a scanning medium. A developing device having a developing roller 903 that attaches a charged toner to a latent image to make a visible image, a toner cartridge 904 that supplies toner to the developing roller 903, and the toner remaining on the photosensitive drum 901 are scraped and stored. A cleaning case 905 is disposed. As the optical scanning device 900, the optical scanning device of each of the above embodiments or other optical scanning devices is used, and the photosensitive drum 901 forms a latent image simultaneously on a plurality of lines for each surface by exposure by the optical scanning device 900 as described above. Is done. The recording paper is supplied from the paper supply tray 906 by the paper supply roller 907, is sent out by the registration roller pair 908 in accordance with the recording start timing in the sub-scanning direction, and is transferred to the toner by the transfer charger 906 when passing through the photosensitive drum 901. The toner is fixed by the fixing device 909 and is discharged to the paper discharge tray 910 by the paper discharge roller 912.
In the sixth embodiment, the optical scanning device 900 includes the photosensors 101 and 102, the dot position deviation detection / control unit 110, the pixel clock generation unit 10, the image processing unit 130, and the laser drive data generation unit 140. When the unit drives the light source device of the optical scanning device 900 with the laser drive data from the laser drive data generation unit 140, the dot position can be corrected with high accuracy, and a high-quality image can be obtained.

7 and 8 show the state of correction of misalignment in the sub-scanning direction of the color image forming apparatus according to the seventh embodiment to which the present invention is applied.
Usually, since a color image forming apparatus performs optical scanning for each color, the dot position deviation characteristics in the sub-scanning direction have different characteristics for each color. FIG. 7 shows an example of dot position deviation in the sub-scanning direction for each color of yellow, magenta, cyan, and black. The example shown in FIG. 7 is an extreme example. For example, in the case of having such characteristics, correcting the dot positions of all the colors to the sub-scanning positions that are supposed to occur is caused by an increase in correction data amount or correction. Due to the influence of misalignment correction error and the like, it may not always be a good correction. Therefore, in the seventh embodiment, the characteristics of each color show almost the same tendency as shown in FIG. 7, so that the dot position in the yellow sub-scanning direction is set as the reference position for the sub-scanning, and the sub-scanning by yellow optical scanning is performed. Measure the positional deviation amount in the scanning direction in advance, measure the positional deviation in the sub-scanning direction for each color of magenta, cyan, and black, and determine the yellow dot position in the sub-scanning direction based on the measurement results. As described above, correction is applied to the dot positions in the sub-scanning direction of each color of magenta, cyan, and black. In this case, since the amount of correction data is small and the amount of correction is small, it is possible to correct misalignment between each color of yellow, magenta, cyan, and black with high accuracy as shown in FIG.

  In the first and third embodiments in which the light source device is shown in FIGS. 1 and 2, when the amount of dot position deviation in the sub-scanning direction is 1 dot or less, the main light source and the sub-light source both emit light and emit light mainly. It is considered that the light source is lit longer than the auxiliary light source. Therefore, it is considered that the life of the main light source is shorter than that of the sub-light source, and the life of the entire optical scanning device is shortened as it is. Therefore, in the seventh embodiment, the function of the main light source and the sub light source in the fifth embodiment is changed, and the function of the main light source and the sub light source is changed to a specific specific one such as every line scan or every page scan. By changing every timing period, the deterioration of the light source is prevented, the difference in life between the main light source and the sub light source is reduced, and the life of the entire apparatus is extended.

  FIG. 15 shows a tandem color image forming apparatus according to a seventh embodiment of the present invention having image forming means including a photoconductor as a plurality of scanned media. The tandem color image forming apparatus requires separate photoconductors corresponding to cyan, magenta, yellow, and black colors, and the optical scanning optical system as the optical scanning device has a separate optical path corresponding to each photoconductor. Then, exposure is performed to form a latent image. Therefore, the main scanning dot position shift generated on each photoconductor often has different characteristics.

  The seventh embodiment includes a polygon mirror 601, scanning lenses 602 to 605 and 606 to 609, dustproof glasses 610 to 613, photoconductors 614 to 617, light receiving means 618 to 621, folding mirrors 622 to 633, and an intermediate transfer belt 634. . In the seventh embodiment, the optical scanning device includes a polygon mirror 601, scanning lenses 602 to 605, 606 to 609, dustproof glasses 610 to 613, folding mirrors 622 to 633, a polygon motor that rotates the polygon mirror 601, and the like. A plurality of laser beams from four light source devices (not shown) are collectively deflected and scanned by a polygon mirror 601 and exposed through scanning lenses 602 to 605 and 606 to 609, folding mirrors 622 to 633, and dustproof glasses 610 to 613. The bodies 614 to 617 are scanned in the main scanning direction. In the optical scanning device, the polygon mirror 601 is arranged in two stages and the scanning optical system is arranged up and down, and this scanning optical system is arranged facing the polygon mirror 601 as a deflecting unit as a center, so that four scanning surfaces can be obtained. Each scanning optical system corresponding to the surface of a photoconductor 614 to 617 is provided. In each scanning optical system, the light receiving means 618 to 621 respectively guide the scanning laser light reflected by the dust-proof glass 610 to 613 by mirrors disposed on both sides outside the effective angle of view. Receive light. Each scanning optical system is provided with the dot position deviation detection / control unit 110, the pixel clock generation unit 10, the image processing unit 130, and the laser drive data generation unit 140 of the first embodiment, and the laser drive unit is laser driven. The light source device is driven by laser drive data (modulation data) from the data generation unit 140.

  In each image forming unit, each of the photoconductors 614 to 617 is rotationally driven by a driving unit (not shown) and uniformly charged by a charging device (not shown), and then an electrostatic latent image is formed by exposure with the laser beam. Each color toner image is formed by being developed by a developing device (not shown). The toner images of the respective colors on the photoreceptors 614 to 617 are transferred onto the intermediate transfer belt 634 by a transfer device (not shown) to form a full color image. The full color image on the intermediate transfer belt 634 is transferred (not shown). The image is transferred to transfer paper by the apparatus, and the transfer paper is fixed with a full-color image by a fixing device (not shown) and discharged to the outside.

  Further, a pattern image for measurement is formed on the intermediate transfer belt 634 in the same manner as the toner image, and a plurality of sensors provided for each scanning optical system detect the pattern image for measurement and detect each color. Measure the dot position. Each dot position deviation detection / control unit 110 obtains a dot position deviation amount in the main scanning direction from the detection signal of the sensor, generates phase data for correcting the deviation amount, and outputs the phase data to the pixel clock generation unit 10. Each dot position deviation detection / control unit 110 measures in advance the amount of position deviation in the main scanning direction due to yellow light scanning with the yellow dot position in the main scanning direction as a reference position for main scanning. Measure the dot position deviation in the main scanning direction for each color of magenta, cyan, and black, and the dot position in the main scanning direction for each color of magenta, cyan, and black with the dot position in the main scanning direction for yellow as the reference position You may make it apply correction to.

  In the seventh embodiment, it is possible to obtain a high-quality image in which the sub-scanning dot position deviation is properly corrected. In particular, the image quality is effective for the positional deviation in the sub-scanning direction. Thus, an image with good color reproducibility can be obtained.

According to the above-described embodiment, the main scanning and sub-scanning dot position deviation correction device capable of correcting the dot position in the main / sub-scanning direction with high accuracy by the combination of the phase-controllable pixel clock generation circuit 10 and the main light source and sub-light source. Can be realized.
According to the above embodiment, the pixel clock generation circuit 10 can control the phase of the pixel clock in finer steps with a relatively simple configuration, and can perform main scanning dot position correction with higher accuracy. Become.

According to the above embodiment, the total light emission time of the main light source and sub light source per dot is made substantially constant (or constant) for each pixel, so that dot position correction in the main / sub scanning direction can be performed with a simple circuit configuration. It becomes.
According to the above embodiment, the total light emission amount of the main light source and sub light source is made substantially constant (or constant) for each pixel, thereby realizing highly accurate dot position correction in the main / sub scanning direction with a simple circuit configuration. it can.

According to the embodiment described above, the life of the light source can be extended by replacing the main light source and the sub light source at a prescribed timing cycle.
According to the above embodiment, the main scanning dot position deviation correction amount of the sub light source is substantially the same (or constant) as the main scanning dot position deviation correction amount of the main light source, so that the data amount is small and high accuracy is achieved. It is possible to correct the dot position in the main / sub scanning direction.

According to the above embodiment, by using surface emitting lasers configured on the same chip as a plurality of light sources, the efficiency is higher than in the case of using a normal semiconductor laser, thereby reducing power consumption and energy saving. Can be measured.
According to the above embodiment, by providing the image forming apparatus with the means for correcting the main scanning dot position and the means for correcting the sub scanning dot position, an image forming apparatus capable of realizing high definition, high image quality, and energy saving can be configured. .

  According to the above-described embodiment, the configuration for performing dot position correction for other colors in accordance with the amount of dot position deviation for a specific color reduces the amount of memory and corrects main scanning dot position and sub-scanning with a simple circuit configuration. An apparatus for correcting the dot position can be realized.

  According to the above-described embodiment, it is possible to form dots with high accuracy by providing a plurality of surface emitting lasers each having a plurality of lattice-shaped light sources on a chip as a plurality of light sources.

  According to the above-described embodiment, a plurality of scanned light beams deflected by the deflector 601 using the mirror as a light guide unit that guides the light beams deflected by the deflector 601 onto the scanned media 614 to 617. High-definition and high-quality tandem color images with little color misregistration that can correct the pixel positions in the main scanning and sub-scanning directions with high accuracy by using the tandem type that scans the medium 614 to 617 to form an image. A forming apparatus can be realized.

It is the schematic which shows the light source device of this Embodiment 1. It is the schematic which shows the surface emitting laser of Embodiment 3 of invention. It is the schematic which shows the surface emitting laser of Embodiment 4 of this invention. It is a figure which shows the light emission signal of each light source in Embodiment 1 of this invention, and the scanning light quantity when the to-be-scanned medium is scanned in the main scanning direction by the light emission signal of each light source. It is a figure which shows the combination of the light emission amount for each pixel of each light source A, B, and C in Embodiment 2 of this invention. It is a schematic diagram which shows the dot position shift correction | amendment of the subscanning direction in Embodiment 4 of this invention. It is a figure which shows the example of the dot position shift of the subscanning direction of each color. It is a figure which shows the result of the position shift correction | amendment of the subscanning direction of Embodiment 7 of this invention. It is the schematic which shows the light source device of Embodiment 5 of this invention. It is a perspective view which shows the example of the optical scanning device used for embodiment of this invention. It is a perspective view which shows an example of the multi-beam scanning apparatus used for embodiment of this invention. It is the disassembled perspective view and perspective view which show a part of example of the optical scanning device which has a laser array. It is the disassembled perspective view and perspective view which show a part of example of the scanning device which has a surface emitting laser. It is sectional drawing which shows Embodiment 6 of this invention. It is the schematic which shows the tandem type color image forming apparatus of Embodiment 7 of this invention. FIG. 3 is a block diagram illustrating a configuration of a pixel clock generation circuit in the first embodiment. It is a figure which shows the relationship between the phase data of the pixel clock generation circuit, a status signal, control data 1, and control data 2. It is a timing chart showing the operation timing of the pixel clock generation circuit. It is the schematic which shows the general structure of an optical scanning device. It is the schematic which shows the example of a surface emitting laser. It is the schematic which shows the whole structure of the optical scanning device in the said Embodiment 1. FIG. It is a figure which shows the example of the pulse produced | generated by the pulse width modulation circuit in the said Embodiment 1 with image data and a dot image. It is a figure which shows the pattern which gives image data to the light sources A, B, and C using the pulse width modulation circuit in the said Embodiment 1. FIG. FIG. 3 is a block diagram showing an example of a pulse modulation signal generation circuit in the first embodiment. FIG. 6 is a block diagram showing another example of the pulse modulation signal generation circuit in the first embodiment. It is a block diagram which shows the example of the means to replace the function of a main light source and a sublight source in Embodiment 5 of this invention. It is a figure which shows the relationship between shift data and the input / output signal of the said shift register. It is a figure which shows the control data of the main scanning dot position shift given to each pixel in Embodiment 2 of this invention.

Explanation of symbols

10 pixel clock generation circuit 11 high frequency clock generation circuit 12 transition detection circuit 13 control signal generation circuit 14 clock 1 generation circuit 15 transition detection circuit 16 control signal generation circuit 17 clock 2 generation circuit 18 multiplexer 19 control data generation circuit 20 status signal generation circuit 21 Select signal generation circuit 201 Power supply device 204 Polygon mirror 208 Photoconductors 101 and 102 Photo sensor 110 Dot position shift detection / control unit 130 Image processing unit 140 Laser drive data generation unit 150 Laser drive unit 500 Pulse modulation signal generation circuit 501 High frequency clock Generation circuit 502 Modulation data generation circuits 503 and 504 Serial modulation signal generation circuit 505 Shift register

Claims (18)

High-frequency clock generation means for generating a high-frequency clock;
Control data generating means for generating first control data and second control data from phase data indicating the phase shift amount of the pixel clock and a state signal indicating the state of the pixel clock;
First clock generation means for generating a first clock based on the high-frequency clock and the first control data;
Second clock generation means for generating a second clock based on the high frequency clock and the second control data;
A pixel clock generation unit including a clock selection unit that selects one of the first clock and the second clock and outputs the selected clock as a pixel clock; and the first clock generation unit includes:
First detection means for detecting a transition of the first clock;
First control signal generation means for generating a first control signal based on the output of the first detection means and the first control data;
First signal transition means for causing the signal to transition at the first change point timing of the high-frequency clock based on the first control signal and outputting the signal as a first clock; Main scanning dot position correction means for correcting dot position in the main scanning direction based on the phase shift of the pixel clock;
The light source in the optical scanning apparatus for forming an image by scanning a plurality of light beams emitted from the light source on the scanned medium along a scanning direction by a deflector has a plurality of main light sources, and one main light source. A plurality of sub-light sources with respect to the light source, the main light source and the sub-light source comprising sub-scanning dot position correcting means for correcting dot positions in the sub-scanning direction by scanning different scanning lines, The dot position correction device according to claim 1, wherein the light emission timing of the light source is generated based on the pixel clock generation unit. The dot position correction apparatus according to claim 1,
The second clock generation means includes
Second detection means for detecting a transition of the second clock;
Second control signal generation means for generating a second control signal based on the output from the second detection means and the second control data;
Dot position correction comprising: second signal transition means for causing a signal to transition at the second change point timing of the high-frequency clock based on the second control signal and outputting the signal as a second clock. apparatus. The dot position correction apparatus according to claim 1 or 2,
When the light emitted from the main light source and the one or more sub-light sources is scanned on the scanned medium along the main scanning direction by the deflector, substantially the same position in the main scanning direction on the scanned medium is set. For one dot formed by light emission scanning of the main light source and the sub light source, the total light emission time of the main light source and the sub light source constituting one dot is substantially constant for each dot. Dot position correction device. The dot position correction apparatus according to claim 1 or 2,
When the light emitted from the main light source and the one or more sub-light sources is scanned on the scanned medium along the main scanning direction by the deflector, substantially the same position in the main scanning direction on the scanned medium is set. For one dot formed by the light emission scanning of the main light source and the sub light source, the total light emission energy of the main light source and the sub light source constituting one dot is substantially constant for each dot. Dot position correction device. The dot position correction apparatus according to claim 1 or 2,
A dot position correcting apparatus, wherein the functions of the main light source and the sub light source are switched at a prescribed timing cycle. The dot position correction apparatus according to claim 1 or 2,
A dot position correction apparatus characterized in that main scanning dot position shift amounts of the main light source and the sub light source constituting one pixel are made substantially the same data. The dot position correction apparatus according to any one of claims 1 to 6,
The dot position correction apparatus according to claim 1, wherein the plurality of light sources use surface emitting lasers configured on the same chip. In an optical scanning device that forms an image by scanning a plurality of light beams emitted from a light source on a scanned medium along a scanning direction by a deflector,
High-frequency clock generation means for generating a high-frequency clock;
Control data generating means for generating first control data and second control data from phase data indicating the phase shift amount of the pixel clock and a state signal indicating the state of the pixel clock;
First clock generation means for generating a first clock based on the high-frequency clock and the first control data;
Second clock generation means for generating a second clock based on the high frequency clock and the second control data;
A pixel clock generation unit including a clock selection unit that selects one of the first clock and the second clock and outputs the selected clock as a pixel clock; and the first clock generation unit includes:
First detection means for detecting a transition of the first clock;
First control signal generation means for generating a first control signal based on the output of the first detection means and the first control data;
First signal transition means for causing the signal to transition at the first change point timing of the high-frequency clock based on the first control signal and outputting the signal as a first clock; Main scanning dot position correction means for correcting dot position in the main scanning direction based on the phase shift of the pixel clock;
The light source has a plurality of main light sources, and has a plurality of sub light sources for one main light source, and the main light source and the sub light source scan on different scanning lines to thereby change dot positions in the sub scanning direction. An optical scanning device comprising: a sub-scanning dot position correction unit that performs correction, wherein the light emission timing of each light source is generated based on the pixel clock generation unit. The optical scanning device according to claim 8.
The second clock generation means; second detection means for detecting a transition of the second clock;
Second control signal generation means for generating a second control signal based on the output from the second detection means and the second control data;
And a second signal transition means for causing the signal to transition at the second change point timing of the high-frequency clock based on the second control signal and outputting the signal as a second clock. . The optical scanning device according to claim 8 or 9,
When the light emitted from the main light source and the one or more sub-light sources is scanned on the scanned medium along the main scanning direction by the deflector, substantially the same position in the main scanning direction on the scanned medium is set. For one dot formed by light emission scanning of the main light source and the sub light source, the total light emission time of the main light source and the sub light source constituting one dot is substantially constant for each dot. Optical scanning device. The optical scanning device according to claim 8 or 9,
When the light emitted from the main light source and the one or more sub-light sources is scanned on the scanned medium along the main scanning direction by the deflector, substantially the same position in the main scanning direction on the scanned medium is set. For one dot formed by the light emission scanning of the main light source and the sub light source, the total light emission energy of the main light source and the sub light source constituting one dot is substantially constant for each dot. Optical scanning device. The optical scanning device according to claim 8 or 9,
An optical scanning device, wherein the functions of the main light source and the sub light source are exchanged at a prescribed timing cycle. The optical scanning device according to claim 8 or 9,
An optical scanning device characterized in that main scanning dot position shift amounts of the main light source and the sub light source constituting one pixel are set to substantially the same data. The optical scanning device according to any one of claims 8 to 13,
An optical scanning device characterized in that the plurality of light sources use surface-emitting lasers configured on the same chip.   An image forming apparatus comprising the dot position correction device according to claim 1 or the optical scanning device according to any one of claims 8 to 14.   A dot position correction device according to any one of claims 1 to 7 or an optical scanning device according to any one of claims 8 to 14, wherein a color image is formed by superimposing a plurality of color images. A color image forming apparatus, wherein a main scanning dot position correction and a sub scanning dot position correction of each image of another color are performed on the basis of a positional deviation amount of an image of a specific color.   A color image forming apparatus comprising a plurality of color image forming units having the dot position correcting device according to any one of claims 1 to 7 or the optical scanning device according to any one of claims 8 to 14. The color image forming apparatus is characterized in that the plurality of light sources use a plurality of surface-emitting lasers each having a plurality of lattice-shaped light sources on a chip for each color. A color image forming apparatus comprising a plurality of color image forming units having the dot position correcting device according to any one of claims 1 to 7 or the optical scanning device according to any one of claims 8 to 14. There,
A tandem type that forms an image by scanning the plurality of scanned media with the light beam deflected by the deflector using light guide means for guiding the light beams deflected by the deflector onto the plurality of scanned media. A color image forming apparatus.

Images